The invention relates to a semiconductor device comprising a semiconductor body with an island-shaped region of a first conductivity type adjoining the surface and surrounded by an isolating region of a second, opposite conductivity type with which the island-shaped region forms a pn-junction, the island-shaped region being covered by an insulating layer on which a contact pad is provided.
Such a device is known from U.S. Pat. No. 3,812,521. This reference describes a device in which the contact pad is separated from a p-type island-shaped region by a silicon oxide layer. The p-type island-shaped region lies in an island-shaped n-type isolating region with which it forms a pn-junction. In the known device, the n-type isolating region is in its turn surrounded by a p-type isolating region which is in electrical contact with the substrate.
It was found in practice that a device of the kind described frequently gives rise to failures in applications for higher voltages. The known device, therefore, has the disadvantage that it cannot be reliably utilized for higher voltages.